U.S. patent application number 13/678223 was filed with the patent office on 2013-05-16 for adaptive radio controlled clock employing different modes of operation for different applications and scenarios.
This patent application is currently assigned to XW LLC dba Xtendwave. The applicant listed for this patent is XW LLC dba Xtendwave. Invention is credited to Oren E. Eliezer.
Application Number | 20130121400 13/678223 |
Document ID | / |
Family ID | 46800747 |
Filed Date | 2013-05-16 |
United States Patent
Application |
20130121400 |
Kind Code |
A1 |
Eliezer; Oren E. |
May 16, 2013 |
ADAPTIVE RADIO CONTROLLED CLOCK EMPLOYING DIFFERENT MODES OF
OPERATION FOR DIFFERENT APPLICATIONS AND SCENARIOS
Abstract
A configurable system and method for a radio controlled clock
(RCC) receiver adapted to apply different strategies for extracting
timing and time information from a phase modulated signal depending
on the type of application the RCC is used in and on the reception
conditions. The official time signal is broadcast from a central
location using a modulation scheme which includes phase modulation
that alternates between different information rates, allowing for
multiple alternative reception modes that are suited for different
ranges of signal-to-interference-and-noise-ratio (SINR). The
operation of the RCC is configured by the application that hosts
it, such that the reception performance and the energy consumption
best suit that application. The reception mode used by the RCC at a
given time may be selected automatically, i.e. without user
intervention, based on the device's profile of operation and the
reception conditions.
Inventors: |
Eliezer; Oren E.; (Plano,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
XW LLC dba Xtendwave; |
Dallas |
TX |
US |
|
|
Assignee: |
XW LLC dba Xtendwave
Dallas
TX
|
Family ID: |
46800747 |
Appl. No.: |
13/678223 |
Filed: |
November 15, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61559966 |
Nov 15, 2011 |
|
|
|
Current U.S.
Class: |
375/238 |
Current CPC
Class: |
G04G 7/02 20130101; G04R
20/10 20130101 |
Class at
Publication: |
375/238 |
International
Class: |
G04G 7/00 20060101
G04G007/00 |
Claims
1. A radio receiver method, said method comprising: receiving a
phase modulated (PM), pulse width modulated (PWM)/amplitude shift
keyed (ASK) broadcast signal encoded with phase-modulated time
information frames; extracting said time information frames from
the phase of said received signal; and operating said radio
receiver in accordance with a predefined profile adapted for a
particular type of application host.
2. The method according to claim 1, wherein at least one input
parameter from said application host is adapted to select a profile
of operation from a plurality of predefined profiles of
operation.
3. The method according to claim 1, wherein each said profile is
adapted to suit the common needs and constraints found in different
types of devices.
4. The method according to claim 1, wherein said time information
frame and said step of extracting enable said radio receiver to use
the received signal differently depending on the reception
conditions experienced thereby.
5. The method according to claim 1, wherein said broadcast signal
comprises multiple representations for timing and time information
provided alternately such that the information can be extracted
from said broadcast signal in a manner optimal to the application
host and the signal to interference and noise ratio (SINR)
experienced by said radio receiver.
6. The method according to claim 1, wherein said broadcast signal
comprises multiple representations for timing and time information
provided simultaneously such that the information can be extracted
from said broadcast signal in a manner optimal to the application
host and the signal to interference and noise ratio (SINR)
experienced by said radio receiver.
7. The method according to claim 1, wherein said profile selected
is operative to optimize operation of said radio receiver based on
reception conditions.
8. The method according to claim 1, wherein said profile selected
is operative to optimize operation of said radio receiver based on
a cost function that includes factors of importance for said
particular type of application host.
9. The method according to claim 8, wherein said factors are
selected from the group consisting of energy consumption, speed of
acquiring the time from the received signal, timing accuracy, and
probability of error in the extracted information.
10. The method according to claim 1, wherein said profile comprises
a wrist-watch profile adapted to configure said radio receiver to
minimize the frequency and duration of reception.
11. The method according to claim 1, wherein said profile comprises
a car profile adapted to configure said radio receiver to attempt
reception relatively frequently and permit reception in an extended
reception mode.
12. The method according to claim 1, wherein said profile comprises
an appliance profile adapted to configure said radio receiver to
operate at a high duty cycle and permit reception in an extended
reception mode.
13. A radio controlled clock (RCC), comprising: a receiver coupled
to an application host, said receiver operative to receive a phase
modulated (PM), pulse width modulated (PWM)/amplitude shift keyed
(ASK) broadcast signal encoded with phase-modulated time
information frames, and extract said time information frames from
the phase of said received signal; and at least one profile adapted
to operate said receiver in accordance with one or more parameters
optimized for a particular type of application host.
14. The radio controlled clock according to claim 13, wherein said
profile selected is operative to optimize operation of said RCC
based on reception conditions.
15. The radio controlled clock according to claim 13, wherein said
profile selected is operative to optimize operation of said RCC
based on a cost function that includes factors of importance for
said particular type of application host.
16. The radio controlled clock according to claim 15, wherein said
factors are selected from the group consisting of energy
consumption, speed of acquiring the time from the received signal,
timing accuracy, and probability of error in the extracted
information.
17. A radio receiver method, said method comprising: receiving a
phase modulated (PM), pulse width modulated (PWM)/amplitude shift
keyed (ASK) broadcast signal encoded with phase-modulated time
information frames; extracting said time information frames from
the phase of said received signal; operating said radio receiver in
accordance with a predefined profile adapted for a particular type
of application host; and adaptively attempting reception at
multiple different symbol rates allowing for optimized reception
for different conditions.
18. The method according to claim 17, further comprising complying
with constraints set by an operating profile selected by said
application host.
19. The method according to claim 17, wherein said different symbol
rates may be provided simultaneously or alternately.
20. The method according to claim 17, wherein said different symbol
rates carry the same or different amounts of information.
Description
REFERENCE TO PRIORITY APPLICATION
[0001] This application claims priority to U.S. Provisional
Application Ser. No. 61/559,966, filed Nov. 15, 2011, entitled
"Reception of Time Information and Synchronization Information in a
Radio Controlled Clock," incorporated herein by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to the field of wireless
communications, and more particularly relates to a configurable
radio controlled clock receiver adapted to extract timing and time
information from a phase modulated signal.
BACKGROUND OF THE INVENTION
[0003] Radio-controlled-clock (RCC) devices that rely on time
signal broadcasts have become widely used in recent years. A
radio-controlled-clock (RCC) is a timekeeping device that provides
the user with accurate timing information that is derived from a
received signal, which is broadcast from a central location, to
allow multiple users to be aligned or synchronized in time.
Colloquially, these are often referred to as "atomic clocks" due to
the nature of the source used to derive the timing at the
broadcasting side. In the United States, the National Institute of
Standards and Technology (NIST) provides such broadcast in the form
of a low-frequency (60 kHz) digitally-modulated signal that is
transmitted at high power from radio station WWVB in Fort Collins,
Colo. The information encoded in this broadcast includes the
official time of the United States. This also includes information
regarding the timing of the implementation of daylight saving time
(DST), which has changed in the United States over the years due to
various considerations.
[0004] Reception challenges created the need for a new broadcast
format, or communications protocol, for time signal broadcasts,
that would allow for robust reception in various types of
applications under various reception conditions while also being
cost-effective. The new broadcast format, operating in accordance
with the present invention, preserves the amplitude modulation and
pulse-width modulation properties of the legacy time-code
broadcast. This backward-compatibility property ensures that the
operation of legacy devices, is not unaffected by the additional
features offered by the enhanced broadcast format.
SUMMARY OF THE INVENTION
[0005] The present invention is a system and method for an adaptive
and configurable radio controlled clock receiver adapted to extract
timing and time information from a phase modulated signal that, in
one embodiment, is transmitted over a pulse-width
modulation/amplitude-modulated signal. The modulation scheme
employed by the transmitter operating in accordance with the
present invention includes multiple different representations of
phase-modulated time and timing information that are broadcast
alternately to allow for optimized reception at different ranges of
SINR values.
[0006] The configurable system and method is operative to apply
different strategies for extracting timing and time information
from a phase modulated signal depending on the type of application
the RCC is used in and on the reception conditions. The official
time signal is broadcast from a central location using a modulation
scheme which includes phase modulation that alternates between
different information rates, thereby allowing for multiple
alternative reception modes that are suited for different ranges of
signal-to-noise-and-interference-ratio (SINR). The operation of the
RCC is configured by the application that hosts it, such that the
reception performance and the energy consumption best suit that
application. Different profiles of operation are defined for
different types of applications, such that an appropriate one is
selected in the RCC in accordance with an indication of
application-type that is provided by the host (e.g., wrist-watch,
microwave oven, car clock). The reception mode used by the RCC at a
given time may be selected automatically, i.e. without user
intervention, based on the device's profile of operation and the
reception conditions.
[0007] There is thus provided in accordance with the invention, a
radio receiver method, said method comprising receiving a phase
modulated (PM), pulse width modulated (PWM)/amplitude shift keyed
(ASK) broadcast signal encoded with phase-modulated time
information frames, extracting said time information frames from
the phase of said received signal, and operating said radio
receiver in accordance with a predefined profile adapted for a
particular type of application host.
[0008] There is also provided in accordance with the invention, a
radio controlled clock (RCC), comprising a receiver coupled to an
application host, said receiver operative to receive a phase
modulated (PM), pulse width modulated (PWM)/amplitude shift keyed
(ASK) broadcast signal encoded with phase-modulated time
information frames, and extract said time information frames from
the phase of said received signal, and at least one profile adapted
to operate said receiver in accordance with one or more parameters
optimized for a particular type of application host.
[0009] There is further provided in accordance with the invention,
a radio receiver method, said method comprising receiving a phase
modulated (PM), pulse width modulated (PWM)/amplitude shift keyed
(ASK) broadcast signal encoded with phase-modulated time
information frames, extracting said time information frames from
the phase of said received signal, operating said radio receiver in
accordance with a predefined profile adapted for a particular type
of application host, and adaptively attempting reception at
multiple different symbol rates allowing for optimized reception
for different conditions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The invention is herein described, by way of example only,
with reference to the accompanying drawings, wherein:
[0011] FIG. 1 is a high level block diagram illustrating a
receiving device operating in accordance with the present invention
within a hosting application;
[0012] FIG. 2 is a high level block diagram illustrating an example
receiver;
[0013] FIG. 3 is a high level flow diagram illustrating how the
reception operation in the receiving device is controlled in
accordance with the operating profile selected by the host; and
[0014] FIG. 4 is a flow diagram illustrating an example cycle of
reception attempts that includes all reception modes (i.e. data
rates);
DETAILED DESCRIPTION OF THE INVENTION
[0015] A high level block diagram illustrating an example receiving
device operating in accordance with the present invention within a
hosting application is shown in FIG. 1. The time keeping device,
generally referenced 100, comprises a host environment that may
represent a microwave oven, car, wall-clock, watch or any other
device where the receiver 120 of the present invention may be
incorporated. The host controller 110 is operative to inform the
receiver through a control bus 130 what type of operation profile
is preferred. Alternatively, such information may be hardwired such
that the receiving device is either pre-programmed to use a
specific operating profile for this hosting application or reads
the selected operating profile from an input port that has a fixed
word applied to it externally, such that no input would be
necessary from the host controller.
[0016] The receiver 120 provides the host with time and timing
information through a communications bus 140, which may be serial,
parallel or wireless. Additional information that may be conveyed
from the receiver to the host through this bus could include
received messages and receiver status notifications (e.g., SINR
conditions).
[0017] A high level block diagram illustrating an example
architecture for the receiver is shown in FIG. 2. The receiver,
generally referenced 200, comprises antenna 210, front end
amplifier 220, analog to digital converter (ADC) 230, digital mixer
250, local oscillator 240, correlator 260 and threshold decision
logic or circuit 270. In this example, digital signal processing is
assumed to be used for the data recovery operation, wherein the
signal from the antenna 210 is first amplified in analog front end
220, then digitized in analog to digital converter 230, then
down-converted by digitally synthesized local oscillator source 240
and multiplication operation 250, such that the correlation or
matched-filtering operation 260 can be performed at baseband.
Decision block 270 decides on the received symbol or word that is
to be presented at output 280, which is provided to the host
application.
[0018] The signal at the transmitter end includes a modulation
scheme having multiple different representations of phase-modulated
time and timing information that are broadcast alternately to allow
for optimized reception at different ranges of SINR values.
[0019] For example, in one representation of timing and time
information, which is tailored for high SINR values, the timing and
time are provided through symbols that are transmitted at a much
higher rate than the 1 bit/sec rate that is used for the legacy
broadcast of the time information. On the other hand, in another
representation that is tailored for very low SINR values, the
symbols of 1 bit/sec are replaced with sequences spanning multiple
minutes in duration, allowing for greater amounts of energy to be
invested in each transmitted symbol, thereby ensuring reliable
reception even at very low SINR values.
[0020] In one embodiment, the information modulated onto the phase
contains a known synchronization sequence, error-correcting coding
for the time information and notifications of daylight-saving-time
(DST) transitions that are provided months in advance.
[0021] The structure and method of operation of the receiver allow
the timekeeping functionality of a device to be accurate, reliable
and power efficient. In one embodiment, the communication protocol
of the present invention is adapted to allow prior-art devices to
operate in accordance with a legacy communication protocol that is
based on amplitude and pulse-width modulations, such that they are
unaffected by the phase modulation that is defined in accordance
with the present invention, whereas devices adapted to operate in
accordance with the present invention benefit from various
performance advantages.
[0022] Although this backward-compatibility property of the
communication protocol of the present invention may represent a
practical need when upgrading an existing system, the scope of the
invention is not limited to the use of this modulation scheme and
to operation in conjunction with an existing communication
protocol.
[0023] The performance advantages offered by the present invention
include (1) greater reception robustness in the presence of impulse
noise and on-frequency jamming; (2) more reliable operation at a
much lower SINR; (3) faster acquisition of the timing and time
information when SINR conditions permit; (4) possibility of
extracting timing more accurately when SINR conditions permit; and
(5) reduced energy consumption, which leads to extended battery
life in battery-operated devices.
[0024] Furthermore, the system is scalable in that it allows for
receivers experiencing different reception conditions to use the
received signal differently. In particular, the broadcast signal
includes different representations for the timing and time
information, that are provided simultaneously or alternately at
different symbol rates, such that it could be extracted from the
broadcast signal in a manner that best suits the application in
which the RCC is embedded and the SINR conditions experienced by it
at a given instance.
[0025] The features described supra serve to greatly increase the
robustness and reliability of the RCC devices embedded in various
applications and environments, such as in wrist-watches,
wall-clocks, cars and microwave ovens, by allowing them to reliably
operate at a wide range of SINR values, while also meeting the
constraints defined by the application, such as minimized energy
consumption or enhanced accuracy requirements.
[0026] An integrated circuit (IC), or other realization of the RCC
in accordance with the present invention, allows for at least one
input parameter from the application hosting it to define its
selected profile of operation from amongst several predefined
profiles of operation that were designed to suit the common needs
and constraints found in different types of devices (e.g., energy
constrained operation in battery operated devices versus reliable
and accurate timing and unconstrained energy consumption in another
type of application).
[0027] In one embodiment of the invention, the various operating
parameters of the RCC may be provided individually by the
application, instead of selecting a specific operation profile, for
which a set of parameters would already be predefined (e.g., the
periodicity and duration of receptions, the targeted symbol rate
for reception, the need for date information, the need for
dual-antenna based reception).
[0028] In general, for a particular application, the time between
consecutive adjustments (i.e. the reception period) and the
reception duration would depend on the allowable timing drift and
current consumption in that application.
[0029] Examples of possible different profiles of operation for a
RCC designed in accordance with the present invention include:
wrist-watch, wall-clock, alarm-clock, car, and appliance (e.g.,
oven). Possible properties of some of these operating profiles are
listed below, alongside with their reasoning:
[0030] 1. Wrist-watch--receive as infrequently as possible (e.g.,
once a week) to conserve energy. Between consecutive receptions
possibly perform timing corrections based on estimated timing
errors. Employ single antenna reception, as the device is not
assumed to be stationary and may be given reception opportunities
at different orientations. Limit reception to fast mode at night,
in order to minimize the duration of synchronization. When
repeatedly failing, move up to normal mode (1 bit/sec), but not to
extended reception mode.
[0031] 2. Car--attempt to receive frequently (e.g., once a day), as
there is no energy constraint. Allow reception at extended
reception mode (sequences spanning multiple minutes) when the
higher rate modes repeatedly fail. Employ single antenna reception,
as the device is not assumed to be stationary and may be given
reception opportunities at different orientations.
[0032] 3. AC Appliance such as microwave oven--the receiver may
operate at high duty cycle and consume more energy. Extended
reception mode may be allowed and will likely be needed for indoor
reception, particularly during the daytime. Device may employ
dual-antenna reception, as it is stationary and placed indoors.
[0033] It is noted that different types of time-keeping
applications, e.g., a clock in a microwave oven versus a
wrist-watch, have different needs and constraints, one of which may
be energy limitation as a result of battery-based operation. This
calls for an operation strategy that is tailored for each type of
application and is designed to effectively address its needs. For
example, a battery operated application such as a wrist-watch,
where energy consumption poses a constraint, may be configured such
that reception is made as infrequent as possible and its duration
is minimized, whereas an application operating off the mains AC
power, such as a microwave oven, may be permitted to attempt
reception more frequently and for longer duration, whenever this
offers performances benefits or even whenever it does not.
[0034] Furthermore, the operation of the time-keeping device would
ideally be optimized based on the reception conditions, such that
for a given reception scenario, characterized by a specific
signal-to-interference-and-noise (SINR) ratio, the receiver would
offer the best possible performance based on a cost function that
considers those factors that may be of importance in that
application (e.g., energy consumption, speed of acquiring the time
from the received signal, timing accuracy, and probability of error
in extracted information).
[0035] With the broadcast format of the present invention offering
multiple representations of the transmitted information, the
receiver is provided with different alternative methods for
extracting the timing and time information from the received
signal, each of which is tailored to a different range of SNIR
values.
[0036] A simplified flow diagram illustrating the basic decisions
made in the receiving device in response to the selected profile of
operation is shown in FIG. 3. A sequence of operations representing
an example embodiment of the method of the present invention starts
with the identification of the selected operating profile, based on
information from the host environment, which may be provided by
means of hardwiring, a user input or a control command that is sent
via a control bus (step 310). In this step, the receiver sets
values for its operating parameters, such as the time between
reception attempts, how frequent the tracking operations may be
(i.e. timing-drift compensation based on reception of a known
sequence in the broadcast signal), what reception modes to use
(i.e. fast/normal/extended) and how/when to report results to the
host (step 320).
[0037] At the appropriate instance, either scheduled or forced, the
receiver attempts reception in reception-attempt (step 330), after
which a decision will be made regarding the result of this attempt
(step 340), based on parameters that are derived from the selected
operating profile. If the reception is considered successful in
evaluation step 340, the result of the reception is reported to the
host (step 370) and the next reception operation, typically for
tracking purposes (i.e. only to compensate for timing drift) will
be scheduled in scheduling (step 380).
[0038] If the evaluation (step 340) determines that the reception
attempt was not successful, another such reception attempt (i.e.
either for tracking or for acquisition of new information) is
scheduled (step 350) based on the set of operating parameters that
correspond to the selected operating profile. This includes not
only the timing for the next reception attempt (e.g. in how many
minutes or hours is another attempt to be made) but also the
reception mode that is to be used (e.g., normal 1 bit/sec reception
or extended reception, wherein each symbol extends over several
minutes). Reception timing step (step 360) determines whether it is
time for the next reception based on a previously scheduled
reception attempt or on an input from the host, and accordingly
invokes such reception (step 330), while using the appropriate
operating parameters that are dictated by the operating
profile.
[0039] A sequence of operations representing an example embodiment
of a portion of the method of the present invention is shown in
FIG. 4. The sequence of operations may represent the
reception-attempt (step 330) shown in the flow diagram of FIG. 3,
and, as such, may be implemented as a function that is called by
the general reception sequence at step 330.
[0040] In this example method, the reception attempt is shown to
start in high-rate reception (step 410) with the highest symbol
rate, e.g., 100 bits/sec, for which a high SINR would be required
for successful recovery of the information from the broadcast
(either time and timing information or a message). If reception at
the high-rate is determined as unsuccessful (step 420), a
normal-mode reception attempt (step 430), e.g., at the lower rate
of 1 bit/sec, may be triggered, following which another evaluation
operation (step 440) determines whether the last reception attempt
was successful.
[0041] In another embodiment of the method of the present
invention, multiple reception attempts at a high rate may be
repeated before the receiver reverts to reception at a lower rate.
If evaluation step (step 440) determines that reception at the
normal data rate is unsuccessful, and if the selected operating
profile for the receiver permits, the receiver attempts reception
at the lowest symbol rate in an extended mode reception attempt
(step 450), e.g. at a rate of 1 symbol/minute, for which reception
may be possible at the lowest SINR values. In a concluding
reception evaluation step (step 460) the outcome of the reception
attempt is evaluated, and if determined successful and reliable,
the reception sequence of operations ends and the reception result
is made available. Alternatively, if the reception is considered
unsuccessful, the receiver may start a new cycle of attempts which
may include the higher rates of reception as well.
[0042] The reasoning behind reception attempts at high rate that
follow failed reception attempts at lower rates, which are
generally capable of receiving at lower SINR, is the following: the
reception conditions may vary over time, as the propagation of
signals broadcast at low frequencies can depend on the ionosphere,
whose properties vary over the course of a day. Additionally,
non-stationary interference may vary over time, such that a
strongly interfered instance may not represent the SINR that may be
experienced at a later instance, and furthermore, certain types of
interference, e.g., strong impulses that appear every few seconds,
may be more detrimental to victim signals that have longer symbol
durations, whereas a repeated message at a high symbol rate may
have a chance of being received in between such interfering
pulses.
[0043] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, and/or components, but do not preclude
the presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof.
[0044] The corresponding structures, materials, acts, and
equivalents of all means or step plus function elements in the
claims below are intended to include any structure, material, or
act for performing the function in combination with other claimed
elements as specifically claimed. The description of the present
invention has been presented for purposes of illustration and
description, but is not intended to be exhaustive or limited to the
invention in the form disclosed. As numerous modifications and
changes will readily occur to those skilled in the art, it is
intended that the invention not be limited to the limited number of
embodiments described herein. Accordingly, it will be appreciated
that all suitable variations, modifications and equivalents may be
resorted to, falling within the spirit and scope of the present
invention. The embodiments were chosen and described in order to
best explain the principles of the invention and the practical
application, and to enable others of ordinary skill in the art to
understand the invention for various embodiments with various
modifications as are suited to the particular use contemplated.
* * * * *